decalescent
by bravevulnerability
Summary: 'He read that body heat helps in these situations.' Season 4 AU.
1. Chapter 1

**A/N: Based on a prompt from the castlefanficprompts tumblr page. If you follow me on tumblr, you've likely already read this, but since deciding to make it a two (possibly three?) shot, I figured it would be easier to post both parts here. **

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><p><em>prompt: Beckett falls through a crack in ice into a freezing river. Castle gets her out and tries to keep her warm before help arrives. Pre-Caskett.<em>

Set mid season 4

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><p>"Castle, don't come any closer," she snaps, the ice already crackling under her feet, but she can see him in the corner of her eye, inching closer despite her orders. "<em>Rick<em>."

He pauses at the soft plea of his name. This ice is going to crack, she knows she's going under into the freezing river water within a matter of seconds, but she is not taking him with her.

"Just let me get to you," he tries again, the same words he's been repeating for the last ten minutes, but his weight will sink them both.

It's her own fault they're in this predicament. She was the one who chased after the suspect when he bolted from the car they had been following and raced across the frozen river. But their guy had misjudged the thickness of the ice and he hadn't made it across, the ice collapsing under his feet once he was only a few steps from the other side. Kate had frozen when the suspect had fallen through the hole and that's when she had felt the patch of ice she's currently standing on start to give.

She didn't tell Castle at first, didn't want to alarm him. She merely instructed for him to call for backup, but when she didn't return from her place in the middle of the river… he knew.

"Kate, please."

"No," she croaks, but he's already slipping to his knees in the snow on the river bank, onto his stomach, belly crawling across thin ice for her.

_Dammit, Castle. _

"Don't," she growls at him, but he keeps coming, all of his concentration on getting across the width of the river, all of his focus on getting to her. "Castle-"

The ice splinters beneath her feet. He stills. She meets his horror filled eyes for just a split second before she goes under.

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><p>"Kate!" He's screaming her name, shouting it over and over again even though it does either of them no good.<p>

Her fingers are still curled around the edges of the hole she's fallen through, her nails cutting into the ice floor and he can see just the top of her head fighting to stay above the current, but nothing else. He's trying not to imagine how cold she must be, how much agony her body must be enduring against the rush of the frigid water, but ever since the freezer incident - god, the freezer. It had taken each of them so long to get past the random shivers that had rattled their bones each day during that case, to stop feeling the lingering touch of ice in their veins - he's done more research than he would ever need on hypothermia. He knows far too well what cold like this can do to a person's body.

He has to get her out of there.

But he can't go any faster. His weight, even lying down, is too much for the sheet of ice covering the river that seems like its grown an eternity in width. He'll be lucky if he can get her out without drowning them both.

"Beckett, just hold on," he tells her, just a few feet away. Just a few more feet.

The ice around the hole isn't reliable, but the layer he's currently splayed across seems sturdy enough, not cracking under him, and Castle reaches out for her.

But he isn't close enough, his fingers just barely skirting Kate's.

He wiggles forward another few inches, feels the ice beneath his chest threaten to give, and he winces, but it stays and he grabs Kate's wrist.

It's been maybe a minute since she's gone under, her fingers' death grip on the ice the only thing keeping her body from being swept away with the current like their suspect, but as soon as he has hold of her arm, she lets go, her grip going limp and _no, Kate, no no no._

He uses all of his strength to haul her out of the water. The ice begins breaking apart underneath his torso, but he drags them both away from it, risking the danger of standing so he can move quicker, find solid ground before they both sink.

By some miracle - God, karma, the universe, he doesn't care which - he makes it with her in his arms to the other side, nearly collapsing in relief when he steps foot on the snow covered ground. But there's no time to be grateful, not yet. She isn't out of the woods yet.

He jerks open the back door of her cruiser and gently deposits her onto the length of the backseat before moving to the front door, breathing hard as he starts the engine and immediately turns the heat on. He joins her in the back then, stripping his coat off before doing the same with hers, trying not to look as he removes all of her wet clothing - save for her bra and underwear because she would _definitely_ kill him - and wrapping her in his lightly dampened wool coat.

"Kate," he murmurs, finally crawling in with her, shutting the door behind him and tugging her body into his lap. He unbuttons the front of his shirt, having forgotten to slip a t-shirt on beneath the blue button down he knows she loves, and suddenly he's grateful for the dressing mishap he cursed himself for earlier this morning.

He jerks when he parts his coat enough to hold her bare skin against his naked chest, forces himself to breathe through the chill of her skin seeping into his. He read that body heat helps in these situations and as soon as he knows she's warm enough, he'll bundle her in his coat again, but for now, he has Kate Beckett's freezing skin defrosting against his.

He knows he's crossed a lot of boundaries within a mere minute - undressing her, holding her in his lap - but he'll beg for forgiveness later, right now… right now he just wants her to be okay, to wake up.

"Kate," he calls again, stroking his fingers at her cheek. So cold, her skin is like the ice coating the river. "Beckett, you can't do this to me again."

It's too similar to what they'd gone through earlier in the year with the freezer. Her skin has that same ghostly pallor that's haunted his nightmares and she isn't answering him, isn't responding at all. If it wasn't for the beat of her pulse and the weak pound of her heart against his, he'd be truly terrified.

"Cas-"

His gaze snaps down to her face against his collarbone, to the choked gasp of his name.

"Kate?" He brushes the soaked mop of her hair back, shuddering as it drapes across his shoulder, and brushes his hand along her cheek, hoping to keep her with him. "Hey, hey, stay with me."

Her eyes flutter and then she's staring up at him, gaze full of confusion as her teeth start up a violent chatter and her body joins in with shivers and a bout of coughing that shake them both.

"You - you g-got me out?" she questions, her trembling voice sprinkled with disbelief.

He nods, realizes he's started rocking her back and forth, to soothe himself or her, he isn't sure.

"And - and naked?"

The startled laugh bursts from his lungs.

"No, no, just enough to get you warm, Kate. I swear. I didn't look."

She huffs and even the small puff of air that leaves her lips is chilled.

"Worse than the freezer," she mumbles against his throat, cuddling closer to his skin, and he tightens the arms wrapped around her, makes sure the blanket of his coat is covering as much of her as possible.

"Can you feel all of your fingers and toes?" he asks and immediately feels the flutter of her fingers against his ribs, sees her toes doing the same where they peek out from the edge of their coat blanket.

"Yeah."

"Good," he breathes. "Are you getting any warmer?"

The temperature of the car is becoming almost stifling, but he doesn't dare turn the heat down from full blast. He can't risk the cold creeping in and stealing her away.

"Little - little bit. Not numb."

"Backup should be here soon. They'll have an ambulance with them and I'm sure they'll give you something dry to wear. I really am sorry, Kate, I know it's not my place to-"

"Castle."

"Hmm?"

He glances down as her unsteady fingers curl around the back of his neck, sending a shiver down his spine that is only partially from the chill of her skin. He wants to tell her he loves her again, this time she'd remember for sure, but the soft pressure of her fingers drawing him down, drawing his mouth down to hers silences the thoughts, the worries, everything, and all he can do is cradle her shivering body in his arms and kiss her back.

She sighs through the tremors racking her frame, seeming to ignore them in favor of his lips moving over hers, but even her mouth is cold, freezing from the inside out, and he takes her upper lip between his, attends to the chapped surface of flesh with his tongue before doing the same to the bottom.

The tiny moan that escapes her throat when he slips past the warmed barrier of her lips, the gentle arch of her drying body as his hand slips inside the cocoon of his coat and splay across her ribs, eradicates the lingering tendrils of ice in his blood, sending heat rushing through.

"Thank you," she gasps suddenly, and he pauses, forces his eyes open to see her gazing up at him, her eyes shining a warm hazel.

"What - what for?"

Kate pushes closer, sealing every inch of their exposed skins together.

"For saving my life. Again," she grins, a little shy. It reminds him of the timid behavior he saw when she came over for dinner a couple of months ago, after they'd reunited while he and his mother had been trapped in a bank that had just been blown to pieces.

This, he thinks, this hopeful tenderness lining the features of her face is what keeps him waiting on the opposite side of the wall for her. But as her palm drapes over his cheek and as she looks up at him with unguarded eyes, letting him see it all in a way she never has before, he doesn't know if there's a wall still standing between them at all anymore.

"Kate?"

"After this, after we get back to the precinct and sort all of this out, will you come home with me?"

He stares down at her, wondering if maybe the frostbite has affected her brain.

"Castle," she huffs and shit, did he say that out loud?

"Come home with you?" he echoes.

"There's a lot of things we need to talk about, a lot of things I don't want to put off anymore, don't want to waste time waiting for. Not anymore."

He tries not to smile, tries not to get his hopes up too high, not yet, but he can already feel his face beaming with it. "Yeah?"

She bites her still quivering lip and nods.

"I was also hoping you might want to spend the night keeping me warm."

His eyebrows hitch and a flush - finally, some color coming to her pale skin - spreads over the column of her neck.

The knock on the car window startles them both and Rick glances up, sees the flashing blue and red illuminating the dim grey of the sky.

"Here," he murmurs, helping her sit up straight and buttoning the front of his coat for her without allowing himself a glance at her skin.

"Rick?"

"Yes," he murmurs, realizing he had never given her an answer. A more insistent knock comes against the glass and Castle pulls her forward by the lapels of his coat, pressing a chaste brush of a kiss to her mouth. "I'll keep you warm all night, Kate."


	2. Chapter 2

Gates is pissed when they enter the precinct together.

Kate's wearing an oversized NYPD sweatshirt and a pair of black sweatpants Ryan had bought for her. Castle had offered to make the drive to the nearby convenience store while she had sat in the ambulance with a blanket wrapped tightly around her lower body – because _of course_ they failed to have an extra pair of NYPD sweats on hand - he has her size memorized already and he had hoped to grab her some coffee as well, but she had grabbed his wrist when he'd risen from beside her, given him a pleading look he had never seen her wear before, and Ryan had stepped forward to volunteer.

"Detective Beckett, my office."

"Sir, would you mind if I changed-"

"_Now_."

Castle watches her fist clench at her side before she nods and strides into her captain's office with her head held high. Castle goes to follow, but Gates narrows her eyes at him and he redirects his path to his chair beside Beckett's desk.

She's in there for a long time, long enough for him to run out of paper clips to add to the foot long chain he's been working on all week, and when the door to Gate's office finally swings open, Kate doesn't make the detour to her desk, heads straight for the elevator, signaling for him to follow with a discrete flick of her eyes and tilt of her head.

"What happened?" he asks once they're enclosed in the lift together.

She huffs, crossing her arms and listing into the back wall of the elevator as the doors slide shut. "Thanks to me, she's instituting a new policy in our department. We're going to have to report our whereabouts at all times while on the job. If I had called in the exact location of where we were going beforehand, backup could have gotten to us quicker and prevented this whole situation."

"I don't know if I agree with the entirety of that," he murmurs, but she merely shrugs.

"Doesn't matter now anyway. So…" He glances up at her, sees the expectant quirk to her eyebrows, the nervous habit of her teeth stabbing into her bottom lip. "Are you still coming over?"

His insides flush with excitement. He had been afraid she might withdraw her request for him to join her tonight, to _keep her warm_, but she looks more sure, more ready, than he's ever seen her.

Castle takes a tentative step forward in the small space, brushing back the kinked curl of her still drying hair before the elevator doors can open up to the precinct's lobby. "Of course."

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><p>Kate drives them to her place, leads him up to her apartment with her brittle fingers loosely twined in his and he follows like a dazed fool, still feeling as though he's waiting for the other shoe to drop, for her to change her mind, but once they're inside her home, she kisses him again. Her fingers curl around his neck and she rises on her toes to reach him, her entire body pressed warm and snug against his, and he can't ignore the sweetness of her mouth, the chapped lips that demand his attention.<p>

It's drugging, a familiar taste that he's been craving for nearly a year. She even makes that same noise when he sucks on her bottom lip, that encouraging little moan that has him clutching her tighter.

She walks him backwards towards her bedroom, smiling against him even as the velvety heat of her tongue layers over his, makes him dizzy. She shivers when his hands slip under the cotton of her sweatshirt, splaying over her lower back, over the planes of her cold flesh. Still so cold.

"You're freezing," he murmurs.

She sighs, knocks her forehead into his as her fingers wind around the fabric of his dress shirt. "Probably will be for a while if memory serves."

He shudders at that, hates even thinking about their past experience with nearly freezing to death.

"Not this time," he decides, stroking his fingers over the knobs of her spine. "Keeping you warm, remember?"

She grins, the brightness of her smile combatting the cold that's seeped into his own skin, and his eyes flicker down as the buttons of his shirt slowly start coming apart for the second time that day.

"Thaw with me," she mumbles, nuzzling her nose against his and directing him past her bed, towards the open door of her en suite.

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><p>The water rises slowly, wisps of steam swirling atop the bath and stretching through the air, fogging up her mirror. Kate's fingers slip to the hem of her borrowed sweatshirt, inching it upwards and slipping it over her head. He reflexively looks away, but she catches him, fingers coming to his chin, palm cradling his jaw.<p>

"Castle, you can look this time."

"Are you sure?" he croaks out, his voice strained from his faltering control, but he has to be positive. He's waited too long to screw this up now. "Because if you aren't ready, I can - I can wait, Kate. I told you I'd wait."

She doesn't respond right away and his stomach somersaults with worry, and then disappointment, because he can wait, he _can, _but god is he tired of waiting.

He considers making a retreat to the kitchen. He could make her some hot chocolate instead. They never specified _how_ he would keep her warm, he could still-

Kate traps his face in her hands, smoothing her thumbs over the cool skin of his ears and forcing him to look at her.

"I want this," she promises, her eyes soft but so solemn as they hold this. "I know we talked about the wall and waiting, but god, Castle." He watches as she shakes her head, looking so tired in that moment, so tired of resisting him and the pull that's always existed between them, but then the fierce gold of her eyes darts up to meet his and the hint of exhaustion dissipates. Determination spills from her gaze, excitement lines the vibrant circles of her irises, and he believes her when she speaks the words, "I want you. And not just for tonight."

Her fingers graze over his belt and her eyebrows arch in question, but he nods, doesn't stop her from unhooking the buckle and pulling the leather from the loops of his pants. Those go next, followed by hers, and they're both in their underwear, staring at one another as steam billows and curls between them, licks at all of the exposed skin.

With her eyes still locked on his, Beckett draws one of her bra straps down and he watches, mesmerized at the roll of her shoulder, the inviting tilt of her neck to one side. His hand reaches forward to sweep her hair back at its own accord and his mouth soon follows, dusting along the bare expanse of flesh, following the hard ridge of her collarbone, allowing his tongue a taste of her skin – the combination of bitter ice and river water failing to mask the distinct flavor of her.

One of her hands is coiled around the front of his boxers, hooked in the waistband, but the other twists around her back, unclasps her bra. The lingerie falls at his feet and he lifts his head from her neck to see her, gloriously naked save for the pair of black underwear still clinging to her skin. But when his gaze lingers at the scar between her breasts, he feels the hesitation radiate from her, senses her hands rising to capture his face, but he leans forward before she can distract him, splays his hands over the cage of her ribs, and brushes his fingers over the surgical scar lining her left side while he presses his lips to the raised circle of flesh above her heart. Remembering the day a bullet pierced the wall of her chest and left her bleeding in his arms will always elicit a sharp ripple of devastation within him, but now, all he can see is proof of her survival, of her strength.

"Tub's almost full," she gasps, slipping her hands to his forearms and tugging gently.

Castle abandons her chest and allows her to draw him back towards the bath of heated water behind her. He sheds his boxers as soon as she shimmies the last piece of black satin from her body, but she pauses before she can step foot in the tub. Her eyes rove his figure for a long moment, long enough to make him feel a flare of self-consciousness, but she doesn't look as if she's judging him, she looks… in awe?

"You're beautiful," she whispers, taking a second to skim her hands along his bare sides, eliciting goosebumps that have nothing to do with the cold.

"Isn't that my line?" he teases, but her eyes are wide, luminous and overwhelming as she stares up at him with the softest smile she's ever worn.

"You're beautiful to me, Castle," she murmurs, lifting on her toes to kiss him once more, painting his mouth with hope and promise and… and yeah, that's definitely love. She loves him and he loves her back whether she truly remembers or not.

He nudges her hips, reminds her of the filling bathtub and holds one of her hands for balance when her lithe leg rises to descend over the edge of the tub. She hisses when she finally dips a foot in the water, her fingers clenching around his while she grits her teeth through the burn, but then her face relaxes and she glances back at him expectantly. Castle steps in beside her, forces himself to breathe through the heat searing his skin, but just like hers, his body adjusts to the temperature within a few seconds and the burn proves a pleasant remedy to the chill of his flesh.

He sits down in the water first, rests his back against the curve of the tub and sighs at the engulfing heat. His brain has been moving at full speed ever since he'd pulled her out of the river, but now, everything slows, relaxes, finds peace. Until she sinks down atop him, her chest to his, her legs folding around him, everything aligned.

"Don't look so panicked," she chuckles, lifting one of her hands from the water to brush his hair back.

"Not panicked," he huffs, gliding his hands down her slick spine, feeling her body hum with pleasure against his. "Still a little dumbstruck," he admits.

Her cheek falls to rest at his chest, just above the wall of the rising water, and she wraps her arms around his submerged torso.

"Over this?" she asks, tracing her nails over his lower back.

"Mm, I just imagined us for so long. Feels surreal."

Her head rotates on his chest, her chin digging into the bones of his sternum as she looks up at him, so peaceful and serene but with an arched eyebrow. "What did you imagine?"

"Kate Beckett wants to hear my fantasies?" he gasps in astonishment and she rolls her eyes, but retracts her arms from his back, uses her hands to inch upwards in the tub, sending water shifting and splashing around the edges.

"No, Castle." Her eyes are dancing, a glimmering green with swirling hints of rich amber and traces of gold bleeding through. "I want to make them come true."

His eyes bulge and she laughs, even as she leans in to nudge her nose against his.

"Don't tease," he grumbles, squeezing at the sharp bones of her hips.

"I'm not teasing," she murmurs while one of her hands slithers downwards, grazing over his abdomen, descending farther until her fingers are curling around him. "Not teasing," she repeats, stroking him slowly, scorching him with her palm. "I'm warming us up."


	3. Chapter 3

**A/N: Please note that the rating has been bumped up to M for this chapter.**

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><p>"You're sure?" he asks, placing a palm to her cheek and skimming his thumb over the papery thin skin beneath her eye as he tries to breathe – the humidity of the air combined with the scalding heat of her hand making it hard to get a steady breath in.<p>

The water sloshes and spills over as she cranes forward to touch her forehead to his, her hand still wrapped around the pulsing length of him, her other splayed over his chest, over the pounding of his heart.

"Yes," she promises, sweeping her lips over his. "I'm in this, Castle."

He reaches forward, turns the running water off before it can overflow completely, and secures a hand at her hip, aiding her balance while she rises on her knees. Her eyes flutter as she teases his tip through her folds, slick with more than water, and he clutches hard at her hipbone, sharing a gasping breath of relief with her when she finally sinks down, takes him deep inside, enveloping him in an all consuming heat.

He runs his fingers up her sides, over her ribs, feels the shiver that travels through her. She's taking a moment to adjust, dropping her forehead to the slippery slope between his neck and his shoulder, and he waits patiently, savoring the narrow, pulsing heat of her engulfing him. But then her hips roll, experimental and slow, and they both groan.

There isn't a lot of room in the tub, but Kate leans forward, drapes her body over his, sealing the warmed planes of their flesh together and it's already more than enough, almost too much. Sensory overload for a body that's been craving hers for so long.

Her arms hook around his neck, folding at his back, and her forehead returns to rest against his once more, the position so intimate, so close, he can't remember the last time he felt comfortable allowing another person to love him like this. But with Kate, the proximity feels right and he meets her gaze, sees her watching him with eyes molten and yearning, as if she's waiting for confirmation.

She holds his gaze as she undulates against him, deliberate this time, and the sparks of pleasure, the frissons of intense heat, burn bright across his body.

"I imagined us too," she tells him, the husk of her voice threading through the scant space between their mouths, and he thinks for a second that she may push him over the edge with her words alone. "I imagined doing this so many times."

Her hips shift and twist over his before she _grinds. _His breath catches in his chest, but it only takes him a moment to plant his feet to the slippery floor of the tub and meet her with a shallow thrust that makes her spine arch. She moans, long and breathless, digging her fingers into his back, and dropping her head to his neck.

The rhythm they find is gentle, a slow back and forth motion that eventually has the waves of cooling water swelling like the tide and lapping against the rim of the tub, eventually flowing over, splashing the wooden floor of her bathroom.

Her lips skim his neck, wet kisses from her warm mouth spreading heat along his throat, across the line of his jaw, and he pants her name, whispers breathless words of encouragement and worship and love against her temple, feeling her control slip more with each syllable that leaves his lips.

It isn't long before her muscles begin to clench around him, hard and tight, and he slips a hand between them, circles her clit, giving her the solid pressure she needs until she's going rigid against him, cresting on the wave of pleasure and breaking against the shoreline of his body with a soft cry. His own release follows all too soon, drowns him, the rippling aftershocks of her orgasm finally pulling him under deep and heavy.

When he emerges, he feels her trembling atop him, the water around them lukewarm now, and he tries to sit up, drain the tub and refill it with another batch of simmering water, but Kate shakes her head, dusting her lips along his clavicle.

"Not cold."

He relaxes back into the slick wall of the tub at that, revels in the warm and loose weight of Kate over him. Her body is like liquid, so pliant and boneless as her breathing finally calms from the short, sharp bursts against his throat, and when she doesn't speak again, he expects her to fall asleep just as he's tempted to.

"You love me?" she hums instead, the words torn between a question and a statement, one he can't refrain from responding to, especially when he knows the confession slipped into her hair only moments ago.

"I do," he murmurs, stroking the wet rope of her hair down her back, feeling her sigh beneath the weight of his palm between her shoulder blades.

The gentle curve of her smile brushes against his throat, traveling upwards until he tilts his head down, offering her the reverent press of his mouth. The caress of her lips, the tease of her tongue in his mouth, elicits a stir between them that has a wicked, satisfied grin tugging her lips upwards.

"It's mutual."

He stills, speechless and uncomprehending, frozen even as her lips continue to work against his at a languorous pace, but at his lack of participation she pauses.

"Castle?"

His body jolts with electricity, his heart filling with joy and disbelief and he stares down at her.

"Really?"

Her eyes soften, traces of sadness pooling in her irises, and she curls her fingers around his ear, stroking the shell with her thumb. "Yeah, Castle. I love you."

He resists the urge to haul her closer, knowing the rush of movement would have another wave of bathwater surging onto her bathroom floor, so he settles for embracing her tightly, resting his cheek atop her head and cradling her body as it relaxes deeper into his, the two of them one sated bundle of twined limbs in the confined space of her bathtub.

"Don't let me fall asleep," she mumbles, using her dripping fingertips to rub at her eyes after a few minutes.

Castle chuckles, blinking away the drowsiness clouding his own eyes. "Why? I'll keep you from sinking under. Good at that, remember?"

The light huff of her laughter against the exposed skin of his chest has him surrendering to a soft shiver.

"I'll dream, nightmares about the cold," she admits, taking a deep breath, her ribs expanding against his, before she grips at the edges of the tub behind him and pushes herself up. She rises from the water shimmering and flushed and the sight has him wanting her all over again. When he fails to follow suit and step out of the bath with her, she notices.

Kate offers him her hand and he sits up in the tub, unplugging the drain on his way out, and smiles when she drapes a towel over his shoulders. "Besides," she murmurs, smiling back at him with a sultry lift of her lips, barely taking the time to dry off before she's dropping the towel and feathering her fingers up his arms, coaxing him closer as she walks backwards towards the bedroom. "I don't want to waste time sleeping."


End file.
